Code:
open chest with 3 rows named "&6&lKøb" to player
wait 1 tick
format slot 0 of player with green wool named "&a&l+" to run [set {crypto.%player%.amount} to {crypto.%player%.amount}+1]->[format slot 1 of player with black wool named "&7&l%{crypto.%player%.amount}%" to close]->[set {_crypto.number.%player%} to 5]
format slot 1 of player with {_crypto.number.%player%} black wool named "&7&l%{crypto.%player%.amount}%" to close
format slot 2 of player with red wool named "&4&l-" to run [set {crypto.%player%.amount} to {crypto.%player%.amount}-1]->[format slot 1 of player with black wool named "&7&l%{crypto.%player%.amount}%" to close]->[set {crypto.number.%player%} to "%{crypto.%player%.amount}% black wool"]